I. Field of the Invention
The present invention relates to a method for manufacturing a multilayer circuit substrate in which wiring layers and insulating layers are alternately laminated on an insulating substrate.
II. Description of the Prior Art
In a conventional multilayer circuit substrate in which wiring layers and insulating layers have been alternately laminated on an insulating substrate formed of ceramics, gold has been used for the wiring layers. Since the gold is expensive, however, it is preferred to employ as wiring layers a less expensive metallic material such as, for example, copper. Usually, a wire bonding process has been employed to bond a lead wire to the uppermost wiring layer in the multilayer circuit substrate. However, the disadvantage to using copper is that the wire bonding process can hardly be applied to copper wiring layers in the multilayer circuit substrate.
The insulating layers of the conventional multilayer circuit substrate have been formed of an organic material, e.g., polyimide. When a semiconductor element such as a large-power LSI was mounted on the multilayer circuit substrate, since such an organic material had improper thermal conductivity, the conventional multilayer circuit substrate which employed the organic material insulating layer had a great drawback in that the heat generated in the semiconductor element could not be rapidly dissipated at its operating time.